The routing has been optimized and the copper routing is fully laid out.

*Instructions:

1. After welding the components, add a heat sink to LM317 to reduce temperature drift.

2. Use a multimeter to connect the module COM and mV interfaces.

3. Move the mV interface of the multimeter to the mA interface, turn on the module power, and adjust the potentiometer so that the current displayed on the meter reaches 100mA.

4. Change the mA interface of the multimeter to the mV interface, and touch the test resistor LCR clips. At this time, the voltage should be 0.000mV. If it is not 0, there is resistance in the test wires, test clips, etc.

5. Start measuring.

*Microresistance meter test principle:

Adjust the potentiometer so that the current flowing through the resistor under test is 100mA. The mV value displayed on the meter can be used to reverse the resistance according to Ohm's law (that is, move the decimal point one place to the right).

1. Microresistance meter, also known as milliohmmeter or microohmmeter, its testing principle is measured through the bridge principle (also known as Kelvin principle) four-wire method, that is, a constant current is applied to both ends of the resistor, and then The voltage at both ends is detected by an instrument, and then the resistance value is automatically calculated by the instrument.

2. Microresistance meter, its testing principle is measured by the four-wire method of the bridge principle.

3. Ordinary multimeters generally use the proportional method to measure resistance. The measured resistor is connected in series with the standard resistor, and the voltage of the standard resistor and the measured resistor is measured. The currents of the two are the same. The resistance of the measured resistor is calculated based on the resistance of the standard resistor.

total cost:

LM317+2.2uF+20Ω metal film resistor+100Ω (3296W) potentiometer＜10 yuan

The attachment contains usage diagrams